It is well known that some insulin-treated diabetic cats may eventually go into remission and no longer require insulin to maintain normoglycemia, probably because in these animals the pancreatic β cells recover their ability to secrete insulin. This is especially likely when newly diagnosed diabetic cats receive early, effective treatment with an appropriate insulin and a low- carbohydrate diet. However, approximately 25-30% of cats who achieve diabetic remission may relapse and again require insulin therapy to maintain normoglycemia.
In this retrospective and prospective cohort study of 21 client-owned cats in diabetic remission (8 female, 13 male, all neutered, age range 5-17 years, representing a variety of breeds) and 28 client-owned healthy control cats (age range 5-18 years, also representing a variety of breeds), the patients were evaluated with fasting blood glucose concentrations and glucose tolerance testing.
All of the diabetic cats in remission had been treated with insulin glargine while diabetic, and most had been fed a low-carbohydrate diet. Control cats were frequency-matched with the diabetic cats based on age and body condition score. All study cats were hospitalized overnight and fasted for 24 hours prior to testing for fasting blood glucose concentration and initiation of the intravenous glucose tolerance test. Following this initial testing, the remission cats were evaluated for relapse by monitoring blood glucose concentrations at home or in the clinic as well as by owner monitoring of clinical signs consistent with diabetes mellitus. At the time of baseline testing, the formerly diabetic cats had been in remission for a median of 107 days (range, 10 days to 4 years), and this was a first remission for all cats in this group.
In the control group, fasting blood glucose concentrations in all cats were less than 117 mg/dL. In the remission group, mean fasting blood glucose concentrations were significantly higher; only 81% (17/21) of the remission cats had fasting blood glucose concentrations < 117 mg/dL. The other four remission cats had fasting blood glucose concentrations ranging from 119 mg/dL to 151 mg/dL. Screening blood glucose concentrations (no specified fasting time prior) were also significantly higher in the remission group compared to the control cats. Most (76%) of the remission cats were found to have impaired glucose tolerance compared to the control cats, all of which demonstrated normal glucose tolerance, based on the results of intravenous glucose tolerance testing.
Twenty of the 21 remission cats were monitored for relapse for at least 9 months after baseline testing, and of these, 30% (6/20) relapsed and became insulin-dependent again. Fasting blood glucose concentrations > 117 mg/dL and three-hour glucose concentrations > 252 mg/dL during the glucose tolerance test were predictive of relapse. Serum fructosamine concentration was found to not be significantly predictive of relapse. Other disease states including severe pancreatitis, gastrointestinal disease, spinal disease, and acromegaly were found in 4 of the 6 relapsing cats within 4 months of relapse, and in several of these cats, corticosteroids had been used to palliate clinical signs. Corticosteroid use in the remission cats was associated with an almost 7 times higher odds of relapse. Five of the non-relapsing cats also had identifiable concurrent diseases, including asthma, renal disease, and hyperthyroidism. Increased feline pancreatic lipase immunoreactivity at the time of testing was not significantly associated with relapse. Age of the patient was also not a significant predictor of relapse. None of the cats with both a normal fasting blood glucose concentration and normal glucose tolerance testing relapsed within a median of 527 days after testing.
Although this study was limited by the small sample size, it demonstrates that continued monitoring of diabetic cats considered to be in remission is essential, as about 30% are likely to relapse. These patients should stay on their low-carbohydrate diets and avoid obesity, as many of these animals, even though in remission, are probably pre-diabetic. Cats in remission with both normal fasting blood glucose concentrations and normal glucose tolerance are not likely to relapse, while those with a fasting blood glucose concentration > 135 mg/dL or with a 3-hour glucose concentration > 252 mg/dL on a glucose tolerance test have hugely increased odds of relapsing within 9 months of testing. Corticosteroid administration should be avoided in all cats in diabetic remission. [PJS]